GLACIERS. As the Alps rise to heights of 13, 000 to nearly 10,000 feet above the sea, in a re gion of ample rainfall, the precipitation on these mountains is great. and gives rise to extensive glaciers, which originate near the summits and descend to different levels, the longest reaching within four or five thousand feet of sea level, and one of them, the Lower Grindelwald, having its termination at an elevation of only 3550 feet. The principal glaciers are found in the Bernese and Pennine Alps, and the group about Mont Blanc, although numerous smaller ones exist in many other parts of the system. The total number is estimated at 1200, of which 471 are in Switzerland and 462 in Austria, those in the former country being by far the largest, covering an area of 710 square miles: the total area of snow and ice in the Alps is about 1600 square miles. The largest and longest of the Swiss glaciers is the Aletsch, in the 13ernese Alps, with a length of 10 miles (area, 50 square miles), and a breadth of ice of more than a mile. In length the Unteraar is next, with a length of 10.4 miles, followed by the Goner in i he Pennine Alps and the Viesch in the Bernese Alps, each of which is 9.4 miles in length. Other well known glaciers are the Mer de Glace, above the Valley of Chamonix, Miage Glacier, which has its source on Mont Blanc, the Oberaar and the Unteraar, in the Bernese Alps, and the Rhone Glacier in the same group. near the Turks Pass.
Our present knowledge of glaciers, their origin, structure, flow, advance, recession, and the phe nomena of erosion. has been mainly derived from a study of these Alpine glaciers. The present glacial system is but the last dying remnant of great ice sheets which once covered•• both flanks of the mountain system. descending to the plains
and valleys on either side. As it shrank, it developed great rivers of ice, which carved mountain gorges and lake ha sins. The lake scenery of the Alps is unrivaled for beauty, grandeur, and diversity. The largest lakes in •lude Geneva, draining into the River Rhone, Neuchatel, Bienne, Thin, Brienz, Lucerne, Zug. Zfirich. Constance, Como. Lugano, Garda, and Maggiore. Tim the high mountains are cirques at the heads of all gorges not now occupied by ice, with little lakelets surrounded by frowning semi circular sweeps of cliffs, hanging valleys, and smooth-sided. U-shaped gorges, planed and pol ished. all bearing mute evidence of their glacial origin. Since the recession of the glaciers. the rivers in their turn have done a vast deal of erosion, hut have not yet by any means effaced from the land She hand-writing of the lee. The main Alpine region is drained on the north by the upper system of the Rhine, includ ing the Aar. and Thum, and by south branches of the Danube, including the Hier, Lech. Isar. 11111. anal ]Eons; on the east by west branches of the middle Danube, She Drave mind Save; on the south by the upper Adriatic coast streams, including the Taglia motto. Piave, Brenta. and Adige. and by the northern branches of the Po, including the Gglio, Adda, Sesia, and Dora Baltia; and on the west by the eastern tributar ies of the lower Rhone, the Durance, Isere, and the upper Rhone itself.